Although organophosphate (OP) pesticide exposures are widespread in our environment, their effect on the health of children is largely unknown. We have enrolled a cohort of pregnant women and followed their children until two years of age to examine the consequences of chronic low-level OP pesticide exposure on the neurodevelopment, growth and respiratory health of young children. CHAMACOS (Center for Health Assessment of Mothers and Children of Salinas, meaning "kids" in Mexican Spanish) is a Community-University partnership serving the agricultural region of the Salinas Valley, California. Participants in the study are predominantly from Latino farmworker families. The children in this cohort are likely exposed to pesticides through the usual pathways such as ingestion of foods with pesticide residues, but, in addition, are exposed to the take-home exposures of farmworker parents and pesticide drift from nearby fields. If there are health consequences of low-level pesticide exposure, they should be most evident in this more exposed population. Preliminary data from the CHAMACOS study suggest that early OP exposure may impact gestational age, neurodevelopment, and Autonomic Nervous System (ANS) functioning. The specific aims of the proposed project are to determine whether OP exposure in utero and/or during the postnatal period is associated at preschool and school-age with: 1) poorer neurodevelopment and behavioral performance; 2) slower somatic growth; 3) atopy, active asthma or asthma-like symptoms, and airway reactivity; and, 4) ANS dysfunction. OP exposure will be defined by levels of six non-specific OP metabolites measured in urine collected from mothers at enrollment, 26-weeks gestation, and postpartum, and from children at 6-, 12-, 24-, 42-, and 60-months of age. We will assess growth and perform a battery ofneuropsychological assessments (e.g., cognition, memory, attention, motor) of the children at 42- and 60-months, and obtain teacher and parent evaluation of behavior and school performance at 84-months. We will assess respiratory health by questionnaire, medical record review, blood analysis of IgE and Thl and Th2 cytokines, and tests of lung function and airway reactivity at 60-months. Due to our strong community partnerships we have successfully maintained this unique cohort, despite the difficulties of conducting a longitudinal study with a migrant farmworker population. This research will enhance our knowledge of the health and development of these hard-to-reach low-income Latino children living in agricultural areas and provide critical information for the U.S. Environmental Protection Agency's implementation of the Food Quality Protection Act.